A conventional loop forming and loosening mechanism 1a of a circular knitting machine, referring to FIGS. 1 and 2, includes a needle cylinder 4a to hold a plurality of needles 5a located vertically, a plurality of correcting troughs 41 above the needle cylinder 4a, a sinker tray 10a located at the circumference of the needle cylinder 4a with a plurality of horizontal sinker grooves 11a formed thereon each holding a sinker 3a, and a cam holder 2a located above the sinkers 3a to hold a plurality of cams 20a. The cams 20a aim to drive the sinkers 3a to move reciprocally and horizontally. Each sinker 3a includes a sliding segment 31a with a sliding portion 310a slidably located in one sinker groove 11a, a loop forming and loosening ancillary segment 32a extended upwards from one side of the sliding portion 310a and then extended outwards and including a horizontal and indented yarn pressing notch 320a to aid each needle 5a in loop forming and loosening, a passive segment 30a located above the sliding segment 31a and driven by the cam 20a with a protrusion 300a extended upwards from the sliding portion 310a, and a correcting segment 34 extended downwards from the loop forming and loosening ancillary segment 32a. The correcting segment 34 is inserted and confined in one correcting trough 41 to aid each needle 5a to accurately form or loosen a loop. Hence when the sinker 3a is moved reciprocally and horizontally the left and right lateral sides and bottom side of the correcting segment 34 generate contact friction due to confinement of the correcting trough 41.
In short, although the conventional technique can aid the needle to form or loosen loops, it still has drawbacks in practice, notably:
1. Each sinker 3a of the conventional loop forming and loosening mechanism 1a of the circular knitting machine has a correcting segment 34, hence the needle cylinder 4a has to form a plurality of correcting troughs 41 thereon during fabrication. This creates structural complexity of the needle cylinder 4a and makes fabrication more difficult. The quality and production yield of the needle cylinder 4a decrease, and material and labor costs increase.
2. When the sinker 3a moves reciprocally and horizontally the correcting segment 34 also moves reciprocally and constantly in the correcting trough 41 that produces a lot of contact friction. This generates high temperature on the sinker 3a during long time of operation, and significant wearing or deformation could happen that shortens the lifespan of the sinker 3a. Moreover, loading of electric power also increases and performance of the loop forming and loosening mechanism 1a suffers. The entire knitting environment also could be contaminated.